Silane-stabilized silicate foams

ABSTRACT

Stable aqueous foams prepared from aqueous solutions of alkaline ionic silicates containing a cationic surface-active onium compound and an alkyl silane, and optionally containing colloidal amorphous silica and a latent acid or salt gelling agent. Rigid foams are obtained by setting the aqueous foams with a salt or acid, then drying the set foam. Inclusion of the silanes increases foamability of the solution, stability of the wet foam, and water resistance and strength of the dried foam.

D United States Patent [151 3,661,602

Gerow 1 May 9, 1972 s41 SlLANE-STABILIZED SILICATE FOAMS 3,493,401 2/1970 Schutt ct al l06/84 [72] Inventor: Sephen A. Gerow' Glen Mills. Pa. 3,549,395 12/1970 Sears et al 106/84 [73] Assignee: E. l. du Pont de Nemours and Company, Primary Examiner-James E. Poer Wflmmgwn, D l- Attorney-Don M. Kerr [22] Filed: July 13, I970 [57] ABSTRACT [2|] App]. No.: 54,573

Stable aqueous foams prepared frcm aqueous solutions of alkaline ionic silicates containing a cationic surface-active :LtSCCll onium compound and an a|ky| silane and optionally Comaim II s colloida amorphous silica and a latent acid or n s g [58] Field of Search l06/74, 84, 75, 40 agent Rigid foams are obtained by semng the aqueous foams with a salt or acid, then drying the set foam. inclusion of the [56] (defences cued silanes increases foamability of the solution, stability of the UNITED STATES PATENTS wet foam, and water resistance and strength of the dried foam.

3. l 36,645 6/ l 964 Dess ..106/75 13 Claims, No Drawings BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to stabilized aqueous fluid or plastic foams of alkaline ionic silicates, such as sodium silicate, and to rigid foams obtained by setting and drying the aqueous foams.

2. Prior Art Before this invention, V. W. Weidman and P. C. Yates discovered that aqueous compositions of alkaline ionic silicates containing a cationic surface-active nitrogen-containing onium compound, and optionally containing colloidal amorphous silica and a latent salt or acid gelling agent such as formamide or ethylene carbonate, could be foamed to provide aqueous fluid or plastic foams. These foams were stable, and generally could be blended with fillers, e.g. perlite or glass fibers, and/or mechanically worked, e.g. pumped, sprayed, or molded, without undue collapse. Further, the foams, (both filled and unfilled) could be set (by action of the latent salt or acid or by treatment with an acidic material such as C0,) and dried, without undue collapse, to provide stable, rigid dried foams. Consequently, the foams were useful in a variety of ways, e.g. as fire-fighting compositions, high-temperature-resistant binders, and low-density heat and sound insulation.

The Weidman and Yates discovery forms the basis for com monly assigned application Ser. No. 779,275 filed in their names on Dec. 2|, 1968.

SUMMARY OF THE INVENTION This invention involves the discovery that inclusion of certain silanes in the foamable compositions just described increases the foamability of the compositions and further stabilizes the wet foams against collapse during mechanical working and drying. Inclusion of the silanes also increases the strength and water resistance of the dried foams. Also, when used at relatively high concentrations (described below) the silanes result in formation of a hard outer layer or crust on a shaped body of the dried foam, thereby increasing its impact strength.

Silanes which can be used to provide these improvements include those of the formula:

R alkyl of one to four carbon atoms or aminoalkyl of one to four carbon atoms, and

R hydrogen or alkyl of one to four carbon atoms.

In the formula, the requirement that b c 2 or 3 assures that there will be at least two hydroxyl groups, or groups hydrolyzable to hydroxyl groups (chloro or alltoxy) attached to the silicon atom. it is believed that the two groups permit the silane to be compatible with the silicate ion.

in one generic embodiment, then, this invention can be defined as an improved aqueous plastic or fluid foam of an alkaline ionic silicate containing a cationic surface-active nitrogen-containing onium compound and a stabilizing amount of a silane of Formula I. The foam optionally also contains colloidal amorphous silica and a latent salt or acid gelling agent.

In another generic embodiment the invention is an imroved rigid foam obtained by setting the aqueous foam of this invention with an acid or salt gelling agent, then drying the set foam. The rigid foam can contain inert solid fillers. The fillers are incorporated into the aqueous foam prior to setting.

DESCRIPTION OF PREFERRED EMBODIMENTS The presently preferred specific embodiments are foams of sodium silicate which contain mineral wool and expanded perlite fillers, hexadecyl trimethylammonium chloride surfactant,

and sodium methyl siliconate [Si(Cl-l,)(OH),(ONa)l stabilizer. For the dried foams, the product compositions (in weight percent) are as follows:

Component Preferred Range Sodium silicate 2 3% l 540% Surfactant 0.4% 02-05% Stabilizer 0.5% 01-20% Water I 0% 0- l 5% Mineral Wool 4% 240% Perlite 63% 40-70% Properly Range Density (lb/RP) ll-l 5 Compressive strength (psi at 5% 30-140 deformation) Thermal conductivity (Btu. inJhr.

ft. F.) at mean temp. of:

GENERAL DESCRIPTION The alkaline ionic silicates which can be used are the watersoluble silicates of monovalent bases which have a basic dissociation constant at 25 C. in excess of 10'. Included among these are the silicates of lithium, sodium, and potassium, and the silicates of strong monovalent bases, such a tetramethylammonium hydroxide, tetraethanolammonium hydroxide, and guanidinium hydroxide. The mole ratio of SiO, to anhydrous basic oxide (e.g. SiO, to Na,0) in the silicates will be between about 3 and 5. SiO, can be present in solutions of alkaline ionic silicates in a mole ratio in excess of 5, but such excess silica will be in the form of colloidal amorphous silica particles, and should be treated as such in calculating compositions.

Colloidal amorphous silica, when used, can be incorporated in the form of an aqueous so] of discrete silica particles in the size range of about 5 to 200 millimicrons. The mol ratio of colloidal silica to silicate ion should be no greater than about 3 to 1, preferably no greater than 2.5 to l.

in preparing mixtures of colloidal silica aquasols with the alkaline ionic silicates of the invention, certain precautions have been found necessary. Generally speaking, alkaline lithium silicates are compatible with virtually any particle size colloidal amorphous silica sol, and in any proportions. This tends also to be true of potassium silicates, tetramethylammonium silicates and tetraethanolammonium silicates. Sodium silicates of mole ratios of silica to Na,O greater than about 4 are also generally compatible with a wide range of particle sizes and concentrations of colloidal amorphous silica, but sodium silicates having lower ratios than this sometimes gel the colloidal amorphous silica, particularly if high concentrations of col loidal amorphous silica and small particle sizes are employed. Guanidine silicate shows somewhat the same problem. This can often be minimized by diluting the colloidal amorphous silica with water or by selecting a larger particle-sized colloidal amorphous silica. In some instances, it may be desirable to add a small additional amount of stabilizing base, such as sodium hydroxide, quanidine hydroxide, etc. to the colloidal amorphous silica sol prior to adding the alkaline ionic silicate. It is usually desirable in doing this to add an amount of strong base which approximately equals in molar concentration the molar concentration of surface silanol groups of the amorphous silica sols.

The total silica content in the foamable compositions and wet foams should be at least 20 percent by weight, based on the weight of water plus alkaline ionic silicate plus colloidal colloidal silica, if any, but cent by weight (same basis).

Cationic surface-active nitrogen-containing onium com- Technology, by Kirk & Othmer, lnterscience Encyclopedia lnc. 1952) in Vol. 9, pp. 592-593. Representative of these compounds are substituted ammonium, imidazolinium, hydroxylammonium and guanidinium compounds in which the substituents are hydrogen, straightor branched-chain aliphatic groups of one to 24 carbon atoms, cycloalkyl, aryl,

the ring in a heterocyclic structure.

Representative of these compounds are: caprylyl trimethyl ammonium chloride (Aliquat 2); oleyl trimethyl ammonium chloride (Aliquat l l oleyl-linoleyl trimethyl ammonium chloride (Aliquat l5); dilauryl dimethyl ammonium chloride (Aliquat 204); lauryl heterocyclic tertiary amine (Amine C); cetyl dimethyl ethyl ammonium bromide (Ammonyx DME); cetyl dimethyl benzyl ammonium chloride (Ammonyx T); lauryl trimethyl ammonium chloride (Arquad 12-50); cetyl trimethyl ammonium chloride (Arquad l6-50); stearyl trimethyl ammonium chloride (Arquad 18-50); quaternized Z-amino pentadecane (Arquad L-lS); dicoco dimethyl ammonium chloride (Arquad ZC-SO); N-cetyl ethyl morpholinium ethosulfate (Atlas O 263); alkenyl dimethyl ethyl ammonium bromide (Barquat OE-SO); lauryl isoquinolinium bromide (Barquat lB-75); myristyl dimethyl benzyl ammonium chloride (BTC i750); stearamido propyl dimethyl B-hydroxtetradecyl quaternary substituted imidazoline of oleic acid (Monaquat OIBC); substituted imidazoline of myristic acid (Monazoline M); coco fatty dialkyl benzyl ammonium chloride (Quatrene CB); fatty glyoitalidinium chloride (Quatrene 0-56); soya fatty dialkyl benzyl ammonium chloride (Quatrene SFB); l-hydroxyethyl 2-heptadecenyl imidazoline hydrochloride (Romine BTQ); and lauryl dimethyl benzyl ammonium chloride (Vantoc CL).

The amount of onium surfactant to be used depends upon the amount of reactive silica" present in the foamable composition. The reactive silica includes the silica in the alkaline ionic silicate plus the silica which is on the surface of the colloidal silica particles (if any) and which is therefore 0.05 can be used, but is unnecessary.

The amount of silane which is effective to stabilize the wet foam and which can be tolerated varies with the particular silane used and the nature and concentrations of other components of the system. For any given system, therefore, the useful range of silane concentrations must be determined by that as little as l part by weight of either sodium methyl stliconate, dimethyl diethoxy silane, or methyl trichlorosilane per thousand parts by weight of aqueous sodium silicate, will produce a stable foam. For some of the silanes, the upper limit is determined by only economics. For example, as much as l.5 parts of sodium sodium silicate can be added gel without foaming. Similarly, methyl trichlorosilane in quantities greater than three parts per 50 parts of sodium silicate causes gelling without foaming.

The foamable composition can also contain a latent salt or acid gelling agent. These are materials which hydrolyze in aqueous solution to liberate an acid or ionized salt. Suitable materials include amides, imides, esters, and acid anhydrides. They can be derived from either organic or inorganic acids. For example, esters of phosphoric and acetic acids can be gelling agents include formamide, ethylene carbonate, ethyl acetate, 2-hydroxy ethyl acetate, and the diacetate and triacetate esters of glycerol. The acidic silicic acid, i.e. have a dissociatlon constant greater than IO". whipping or beating air or another inert, water-insoluble gas, such as a Freon" fluorocarbon, into the composition.

After foaming, but before setting, various inert solid fillers can be incorporated into the foams, in amounts up to about I 5 parts by weight per one part by Representative of suitable fillers are particulate additives such as the various clays including the expanded clay aggregates, expanded perlite and vermiculite, pigmentary potassium titanate, and gypsum; and fibers such as plastic fibers, vegetable fibers such as paper pulp, bleached and unbleached wood pulp, glass fibers, metal fibers, ceramic fibers, mineral fibers such as asbestos, and synthetic inorganic fibers such as rock wool, slag wool, and the alumino-silicate fibers including Fiberfrax" (Carborundum Co.), "Thermoflex (Johns-Manville Co.), and "Kaowool" (Babcock and Wilcox Go). Other suitable additives to the foams of this invention include materials which serve as binding agents such as polymers, including phenol formaldehyde and urea formaldehyde, as well as fugitive organic binders such as sugars, starches, resins, and gums.

and about l2.5. At pH below 9, gelling begins and the composition will not foam satisfactorily.

It is generally desirable to mold the wet foams into desired shapes prior to setting. As indicated above, the foams can be mechanically worked without collapse of the foam bubbles.

if a latent gelling agent is included in the foamable c0mposition, setting can be accomplished generally by letting the wet foam stand at room temperature until the gelling agent hydrolyzes. If desired, setting can be accelerated by heating the foam. Generally, heating beyond about 200 F. is unnecessary.

If a latent gelling agent is not used, setting can be produced by addition of an prematurely,

molding, and molding must be carried out rapidly before setting occurs. For this reason it is preferred to use an acidic gas such as carbon dioxide or sulfur dioxide.

Foams of the invention can contain other ingredients than those already mentioned. For example, various materials which fonn insoluble chemical bonds with the silicate can be included to further increase water resistance. Examples of such materials include magnesium oxide, zinc oxide, fly ash (calcium silicate), Portland cement, and alumino silicate clays.

The foams, both in the wet stage and after setting, are characterized by very fine, uniform, pore structure and low density. Pore diameter is generally no more than i millimeter, and average diameter is usually much less. Densities of both the wet and dried foams range from 3 to 40 lb./ft.. The lower densities are preferred for thermal insulation applications, but the higher densities are preferred for applications in which substantial loads must be borne by the foam. The density of filled bodies bonded by these foams will of course vary with the density of filler material, but the density of the foams themselves fall within the range 3 to 40 lbJfL'.

The wet foams of the invention are stable, even without added filler. They do not collapse and drain on standing in air at ambient temperatures for at least 24 hours.

The dried foams are also characterized by high surface area, in the range 300 to 1,000 m.'/g. as determined by nitrogen adsorption. This makes them desirable as catalyst supports.

Foams of the invention can also be employed either with or without fillers to prepare wall board and ceiling tile, thermal insulation, and sound insulation. The wet foams can be prepared continuously from a foam generator, sprayed on surfaces where insulation is desired, and set and dried in place. They can also be used as fire fighting compositions by blanketing the burning area with the foam.

The following examples will further illustrate the invention. All parts are parts by weight unless other-wise stated.

EXAMPLE I A S-quart Hobart mixer kettle is charged with 87.5 parts of sodium silicate (8.9% Na,0, 29.0% SiO,, 62.1% H,O; of specific gravity 4| .6 Be at 60 F. and having an approximate viscosity of 250 cp. at 78 F.), l2.5 parts ofdistilled water, 2.5 parts of 30 percent sodium methyl siliconate and one part of 50 percent hexadecyl-trimethylammonium chloride. Upon adding the surfactant a white gel is produced. The mixture is blended for ID seconds with a wire-ship beater at low speed and then beat at high speed for l minutes to produce a stable foam. The foam occupies a space 14 times greater than that of the starting mixture. It has a density of 9.8 pounds per cubic foot in this wet state.

To the above foam is added 100 parts of ultra-fine expanded perlite having a density of 2.5 pounds per cubic foot. The mixture is blended for twenty seconds at low speed to produce a low density, viscous mass. Specimens are molded and immediately subjected to an atmosphere of carbon dioxide gas for a period of 5 minutes. Specimens are air-dried for l6 hours and then oven-dried at a temperature of 50 C. for an additional 8 hours. A low density insulation composition is obtained by this procedure, and is characterized as follows:

Density, lb./cu. ft. l4.0

Compressive strength, p.s.i. at l 14 5% deformation Lineal shrinkage on drying, i: 1

Water resistance, 8-hour boil followed by l6-hour immersion:

Loss in volume, 0.25 Density IbJcu. ft. l2 Compressive strength, p.s.i. at 50 5% deformation EXAMPLE 2 percent hexadecyltrimethylammonium chloride. Upon adding the surfactant a white gel is produced. The mixture is blended for seconds with a wire-ship beater at low speed and then beat at high speed for 10 minutes to produce the stable foam. The foam occupies a space fourteen times greater than that of the starting mixture. It has a density of 9.8 pounds per cubic foot in this wet state. To the above foam was added 10 parts of mineral wool and mixed for 1 minute at high speed and I82 parts of ultra-fine expanded perlite having a density of 2.5 pounds per cubic foot. The mixture is blended for seconds at low speed to produce a low density, viscous mass. Specimens are molded and immediately subjected to an atmosphere of carbon dioxide gas for a period of seconds. Specimens are air-dried for 16 hours and then oven-dried at a temperature of 200F. for an additional 8 hours. A low density insulation composition is obtained by this procedure, and is characterized as follows:

The procedure of Example 2 is repeated except that 5 parts by weight of sodium methyl siliconate is omitted. The product is characterized as follows:

Density, lb.lcu. ft.

Compressive strength, p.s.i.

5% deformation Linea] shrinkage on drying, k

foam is blended with parts of ultra-fine perlite powder (2.5 lb./cu.ft. density) together with 40 parts of fly ash. Specimens are formed in a mold and immediately subjected to an atmosphere of carbon dioxide gas for a period of five minutes followed by air-drying for 60 hours.

A rapidly set low density insulation is obtained by this procedure, and is characterized as follows:

Density, lb./cu.ft. 12 6S Compressive strength, p.s.i. at 5| 5% deformation Lineal shrinkage on drying, l

EXAMPLE 5 The procedure of Example 1 is repeated except that two hundred parts of sodium silicate are mixed with 5 parts of 30 percent sodium methyl siliconate and 5 parts of the 50 percent hexadecyl trimethylammonium chloride. The foam expands about 7 times the volume of that of the substituents and has a density of 20 pound per cubic foot. The filled foam is 28.47% SiO processed as in Example I to give a shape which has the following properties:

Density, lb./cu.ft. 25

Compressive strength, p.s.i. at 16] 5% deformation Lineal shrinkage on drying, i: l

EXAMPLE 6 Density, lb.lcu.ft. 3i Compressive strength, p.s.l. at 235 5% deformation Linesl shrinkage on drying, I: 1

EXAMPLE 7 With stirring, 175 parts of sodium silicate (8.7% Nap: 62.9% H,0 of specific gravity 40.6 Be at 60 F. and having an approximate viscosity of 120 cp. at 78' F.) are blended with a mixture consisting of 25 parts of distilled water, l parts of formamide and 0.25 parts of dimethyldiethoxysilane. Two parts of a 50 percent solution of hexadecyl trimethylammonium chloride are added and the mixture is blended for IS seconds in a Hobart mixer kettle. Following this, the mixture is beaten for 8 minutes with a wireship beater at maximum speed to produce a foam. To the foam is added 100 parts of ultra-fine perlite powder (2.5 lb./cu.ft. density) and 10 parts of mineral wool. The filler is blended thoroughly into the foam using the Hobart mixer and paddle. Specimens are formed in a mold and subjected to heat in an oven at 60 C. for 10 minutes.

A quick set low density insulation is procedure, and is characterized as follows:

obtained by this Density, lb./cu.ft. l9

Compressive strength, p.s.i. at I00 deformation Lineal shrinkage on drying, k l

EXAMPLE 8 The procedure of Example 7 is repeated using 175 parts of sodium silicate (8.9% Na,O: 29.0% SiO,: 62. l% H,O) of specific gravity 4| .6 Be at 60 F. and having an approximate viscosity of 250 cp. at 78 F.

As in Example 5, a quick-setting low density insulation product is obtained having the following balance of properties:

Compressive strength, p.s.i. at 100 5% deformation Lineal shrinkage on drying, '5 1 EXAMPLE 9 With stirring, 175 parts of sodium silicate (8.9% Na,0: 29.0% Si0,: 62.1% H,O) are blended with 25 parts of distilled water and 5 parts of gamma aminopropyltriethoxy-silane. Two parts of a 50% solution of oleyl linoleyl trimethylammonium chloride are first slowly blended followed by a fast whipping in a Hobart mixer kettle using a wire-ship beater for 10 minutes. Following this, 130 parts of ultra-fine perlite powder (2.5 lb./cu.ft. density) are blended into the foam using the Hobart mixer kettle and paddle. Specimens are molded and immediately subjected to an atmosphere of carbon dioxide gas for a period ofS minutes.

By this procedure, a quick-setting insulating product is obtained that develops 60 lb.lsq.in. compressive strength at 5 percent deformation within a five-minute period after foaming and is further characterized below:

Density, lb./cu.ft. 25 Lines! shrinkage on drying, I: 1

EXAMPLE 10 The procedure of Example I is repeated using 175 parts of potassium silicate (12.45% K O: 26.25% Si0,: 61.30% 11,0 of specific gravity 40.5 Be at 60' F. and having an approximate viscosity of 325 :i: 75 cp. at 77' F.), instead of the sodium silicate in Example I.

As in Example I, a rapidly-set low density insulation material is obtained that is characterized as follows:

Density, lb./cu.fl. l8 Compressive strength, p.s.l. at 70 5% deformation Linesl shrinkage on drying, 5 1

EXAMPLE 1 l The procedure of Example 1 is repeated, employing the following silicate:

I75 parts of guanidine silicate solution of 3.06 molality (0.924 mol ratio guanidine to silica: 38.6 percent solids: 20.2 percent silica). As in Example I the silicate solution was foamed, filled with perlite, molded and set with C0, to give a shape with insulating properties.

EXAMPLE 12 200 parts of lithium silicate (4.8 SiO,: up on a mole basis at 22 percent solids) are blended with a mixture consisting of 25 parts H,O and 5 parts of 30 percent sodium methyl siliconate. Following this, 5 parts of fi-pentadecyl trimethylammonium chloride are added and the mixture is beaten as previously described in Example I. A filler consisting of I20 parts of ultra-fine perlite (2.5 lb./cu.ft. density) is blended into the foam. Specimens are formed in a mold and immediately exposed to an atmosphere of carbon dioxide gas for a period of five minutes followed by air-drying for sixty hours. A rapid-set insulation product is obtained by this procedure that is characterized as follows:

Density, lb./cu.ft. l9

Compressive strength, p.s.i. at

5% deformation Lineal shrinkage on drying, k l

EXAMPLE l3 With stirring, 150 parts of potassium silicate (20.8% SiO,: 8.3% K,O: 70.9% H,O of specific gravity 30.2 Be at 60 F.) and 50 parts of an ammonium stabilized colloidal silica aquasol containing 30 percent silica of an average particle size of 15 mp, and having a pH of 9.8 and an SiO, to NH, weight ratio of is blended with 5 parts of 30 percent sodium methyl siliconate. Three parts of a 50 percent solution of hexadecyltrimethyl ammonium chloride are added and the mixture is whipped in a Hobart mixer kettle to produce a foam.

A filler mixture consisting of 50 parts of ultra-fine perlite powder (2.5 lb./cu.ft. density) and 50 parts of coarse perlite grains (7 lb./cu.ft. density and 8-20 mesh size) is blended into the foam. Specimens are formed in a mold and immediately subjected to an atmosphere of carbon dioxide gas for a period of 10 minutes before drying in air.

A chemically set low-density insulation is obtained by this procedure, which is characterized as follows:

Density, lb./cu.ft. l5

into a S-quart Hobart mixing kettle is charged 100 parts of sodium silicate (8.9% Na O: 29.0% SiO,: 62.l percent water of specific gravity 4L6" Be at 60 F. and having an approximate viscosity of 250 cp. at 78 F.), 40 parts water, 100 parts Ludox" AS, an ammonia-stabilized colloidal silica aquasol containing 30 percent silica of an average particle size of 13 mp. and having a pH of 9.8 and an NH, to SiO. weight ratio of l:l20, and 5 parts of 30 percent sodium methyl siliconate. This mixture is stirred for 15 seconds at slow speed. Then 3 parts of a 50 percent solution of hexadecyl trimethylammonium chloride are mixed at high speed with a wire-ship beater for minutes. The resulting foam occupies a space ten times that of the substituents and has a density of about 20 |b./cu.ft. The foam has good stability and can be used in many binder applications.

Compressive strength, p.s.i. at 5 5% defonnatlon Lineal shrinkage on drying. I:

EXAMPLE IS The foam of Example 14 is cast in a mold and exposed to carbon dioxide gas for three minutes. A low-density shape having insulating properties is formed.

Density, Ib./cu.ft. 20

Compressive strength,

p.s.i. at 7 5% deformation Lineal shrinkage on drying [0 EXAMPLE l6 The foam of Example 14 is blended with 125 parts of ultrafine perlite having a density of 5 lbs./cu.ft. for 15 seconds at low speed in a Hobart mixer. The filled foam is cast and exposed to carbon dioxide gas for three minutes and then airdried. The shape has the following properties:

Density, lb./cu.ft. 15

Crush strength, p.s.i. at 60 5% deformation Lineal shrinkage on drying, (I

EXAMPLE l7 Example 16 is repeated except that 55 parts of fly ash and 75 parts of ultra-fine perlite powder (2.5 lb./cu.ft. density) are employed in place of the filler. A final shape of comparable properties is obtained.

Density, lb./cu.fi. 15 Crush strength, p.s.i. at 65 5% deformation Lineal shrinkage on drying, I: l

EXAMPLE IS The procedure in Example 16 is repeated except that 20 parts of mineral wool and 90 pans of perlite are substituted for fly ash and perlite. A final shape is obtained of comparable properties.

Density, lbJcuft. l5

Crush strength. psi. at 65 5% deformation Llneal shrinkage on drying, 1: 1

EXAMPLE l9 Density, lb./cu.ft. 20 Corn ressive strength, p.s.i. at 65 5 deformation Linea] shrinkage on drying, I: 1

EXAMPLE 20 175 parts of sodium silicate (8.7% Nap: 28.47% Si0,: 62.9% 5.0 are blended with a mixture of 25 parts distilled water and five parts of 30 percent sodium methyl siliconate. Afier slowly mixing, two parts of a 50 percent solution of hexadecyl trimethyiammonium chloride are added and the mixture is blended for 12 seconds in a Hobart mixer kettle. Following this, the mixture is best for 8 minutes with a wire-ship beater at maximum speed to produce a foam. To the foam are added l5 parts of Fiberfrax" ceramic fiber and a blend of fillers including 75 parts of ultra-fine perlite powder (2.5 lb./cu.ft. density) and 150 parts of Veri-lite" expanded refractory clay particulate aggregate. The fillers are uniformly mixed throughout the foam binder matrix using the Hobart mixer and paddle. Specimens are molded and subjected to CO, gas for 5 minutes and then allowed to dry completely in air.

A hard, strong, tough refractory insulating material is thus produced having the following properties:

Density, lb./cu.ft.

Compressive strength, p.s.i. at

5 5 deformation Lineal shrinkage on drying, '5

EXAMPLE 2] EXAMPLE 22 A foam having a ratio of 75 percent silica to 25 percent silicate is prepared using a S-quart Hobart mixer and a wire-ship beater. 140 parts of "Ludox" AS (an ammonia-stabilized colloidal silica aquasol containing 30 percent silica of an average particle size of 13 my and having a pH of 9.8 and a NH, to SiO, weight ratio of 1.2550) are mixed with ten parts of potassium silicate having an SiO, to K,0 weight ratio of 1.8:1 at a density of 12.5 lb./gal. and 5 parts of 30 percent sodium methyl siliconate. These ingredients are mixed for 10 seconds at low speed in the Hobart mixer. Two parts of a 50 percent solution of trimethylhexadecyl ammonium chloride are added to the mixture and beat for seconds at high speed. A stable foam is obtained which could be filled to produce a low-density thennal insulation material.

Density, Ib./cu.fl. 1.5

Compressive strength, psi. at 0.38

5% deformation Linea] shrinkage on drying, I: I2

EXAMPLE 23 A 5-quart Hobart mixer kettle is charged with 87.5 parts of sodium silicate (8.9% Na,O: 29.0% Si0=z 621% H 0 of specific gravity 4l .6 Be at 60 F. and having an approximate viscosity of 250 cp. at 78 F. 12.5 parts of distilled water 2.5 parts of 30 percent sodium methyl siliconate and l part of 50 percent hexadecyltn'methyl ammonium chloride. Upon adding the surfactant a white gel is produced. The mixture is blended for ID seconds with a wire-ship beater at low speed and then beat at high speed for ID minutes to produce the stable foam. The foam occupies a space fourteen times greater than that of the starting mixture. It has a density of 9.8 pounds per cubic foot in this wet state.

To the above foam was added parts of mineral wool and 91 parts of ultra-fine expanded perlite having a density of 2.5 pounds per cubic foot. The mixture is blended for seconds at low speed to produce a low-density, viscous mass. Specimens are molded and immediately subjected to an atmosphere of carbon dioxide gas. Following this, specimens are aged for a period of at least two weeks under ambient conditions and then oven-dried at atemperature of 200 F. for an additional 8 hours. A low density insulation composition is obat 5% deformation I claim:

1 In a stable, fluid or plastic aqueous foam composed essentially of water, a dissolved alkaline ionic silicate, and a cationic nitrogen-containing surface-active onium compound, the improvement which comprises inclusion of a stabilizing quantity of a silane of the formula where a l or 2 b I 0, l, 2 or 3 c 0, l, 2 or 3 d 0 or I b c 2 or 3 R alkyl of one to four carbon atoms or aminoalkyl of one to four carbon atoms, and

R I hydrogen or alkyl of one to four carbon atoms.

2. An improved foam of claim 1 in which the silane is sodium methyl siliconate, dimethyl diethoxy silane, gammaaminopropyl triethoxy silane. or methyl trichlorosilane.

3. An improved foam of claim 1 in which the silane is sodium methyl siliconate.

4. in a process for making a stable, fluid or plastic aqueous foam by adding a cationic nitrogen-containing surface-active onium compound to an aqueous solution of an alkaline ionic silicate. then foaming the mixture, the improvement which comprises including in the mixture a stabilizing amount of a silane of the formula where a= 1 M2 b=0, 1,2or3

i2 c=0, l, 2or 3 d-0orl a+b+c+d=4 b+c=2 or 3 R alkyl of one to four carbon atoms or aminoalkyl of one to four carbon atoms, and

R I hydrogen or alkyl of one to four carbon atoms.

5. An improved process as defined in claim 4 wherein the silane is sodium methyl siliconate. dimethyl diethoxy silane, gamma-aminopropyl triethoxy silane, or methyl trichlorosilane.

6. An improved process as defined in claim 5 wherein the silane is sodium meth lsiliconate.

'7. In a stable, rigid foam composed essentially of water, a gelled alkaline ionic silicate, and a cationic nitrogencontaining surface-active onium compound, the improvement which comprises inclusion in the foam prior to gellation of a stabilizing quantity of a silane of the formula a I l or 2 b== 0, i, 2 or 3 c- 0, l, 2 or 3 d I 0 or i b c 2 or 3 R alkyl of one to four carbon atoms to four carbon atoms, and

R hydrogen or alkyl of one to four carbon atoms.

8. An improved foam of claim 7 in which the silane is sodium methyl siliconate, dimethyl diethoxy silane, gammaaminopropyl triethoxy silane, or methyl trichlorosiiane.

9. An improved foam of claim 7 in which the silane is sodium methyl siliconate.

10. in a process for making a stable, rigid foam by adding a cationic nitrogen-containing surface-active onium compound to an aqueous solution of an alkaline ionic silicates, then foaming the mixture, the improvement which comprises including in the mixture a stabilizing amount of a silane of the formula or aminoalkyl of one a= l or 2 b=0, l, 2 or 3 c= O, l, 2 or 3 d= 0 or i R alkyl of one to four carbon atoms or aminoalkyl of one to four carbon atoms, and

R hydrogen or alkyl of one to four carbon atoms, then setting the foam with an acid or salt gelling agent, then drying the foam.

11. A improved process as defined in claim 10 in which an inert solid filler is mixed with the aqueous foam prior to setting.

12. An improved process as defined in claim 10 in which the aqueous foam is set with acidic gas.

13. An improved process as defined in claim 10 in which the gas is carbon dioxide.

' i i i i 

2. An improved foam of claim 1 in which the silane is sodium methyl siliconate, dimethyl diethoxy silane, gamma-aminopropyl triethoxy silane, or methyl trichlorosilane.
 3. An improved foam of claim 1 in which the silane is sodium methyl siliconate.
 4. In a process for making a stable, fluid or plastic aqueous foam by adding a cationic nitrogen-containing surface-active onium compound to an aqueous solution of an alkaline ionic silicate, then foaming the mixture, the improvement which comprises including in the mixture a stabilizing amount of a silane of the formula Si(R)a(OR'')b(Cl)c(ONa)d where a 1 or 2 b 0, 1, 2 or 3 c 0, 1, 2 or 3 d 0 or 1 a + b + c + d 4 b + c 2 or 3 R alkyl of one to four carbon atoms or aminoalkyl of one to four carbon atoms, and R'' hydrogen or alkyl of one to four carbon atoms.
 5. An improved process as defined in claim 4 wherein the silane is sodium methyl siliconate, dimethyl diethoxy silane, gamma-aminopropyl triethoxy silane, or methyl trichlorosilane.
 6. An improved process as defined in claim 5 wherein the silane is sodium methyL siliconate.
 7. In a stable, rigid foam composed essentially of water, a gelled alkaline ionic silicate, and a cationic nitrogen-containing surface-active onium compound, the improvement which comprises inclusion in the foam prior to gellation of a stabilizing quantity of a silane of the formula Si(R)a(OR'')b(Cl)c(ONa)d where a 1 or 2 b 0, 1, 2 or 3 c 0, 1, 2 or 3 d 0 or 1 a + b + c + d 4 b + c 2 or 3 R alkyl of one to four carbon atoms or aminoalkyl of one to four carbon atoms, and R'' hydrogen or alkyl of one to four carbon atoms.
 8. An improved foam of claim 7 in which the silane is sodium methyl siliconate, dimethyl diethoxy silane, gamma-aminopropyl triethoxy silane, or methyl trichlorosilane.
 9. An improved foam of claim 7 in which the silane is sodium methyl siliconate.
 10. In a process for making a stable, rigid foam by adding a cationic nitrogen-containing surface-active onium compound to an aqueous solution of an alkaline ionic silicates, then foaming the mixture, the improvement which comprises including in the mixture a stabilizing amount of a silane of the formula Si(R)a(OR'')b(Cl)c(ONa)d where a 1 or 2 b 0, 1, 2 or 3 c 0, 1, 2 or 3 d 0 or 1 a + b + c + d 4 b + c 2 or 3 R alkyl of one to four carbon atoms or aminoalkyl of one to four carbon atoms, and R'' hydrogen or alkyl of one to four carbon atoms, then setting the foam with an acid or salt gelling agent, then drying the foam.
 11. A improved process as defined in claim 10 in which an inert solid filler is mixed with the aqueous foam prior to setting.
 12. An improved process as defined in claim 10 in which the aqueous foam is set with acidic gas.
 13. An improved process as defined in claim 10 in which the gas is carbon dioxide. 